A group of inmates in U.S. prisons has called for a strike to protest mistreatment, bad facilities and the lack of fair wages for the work many are forced to do behind bars.

“All persons imprisoned in any place of detention under United States jurisdiction must be paid the prevailing wage in their state or territory for their labor,” reads a list of demands posted online by the Incarcerated Workers Organizing Committee, one of the groups organizing publicity for the strike, which has been planned to last from Aug. 21 through Sept. 9.

It’s hard to tell how many prisoners are participating in work stoppages since prisons control inmates’ communication with the outside world. Organizers have said there are confirmed strikes in several states, but corrections agencies have insisted nothing is happening.

“There have been no reports of inmate work strikes” in any federal facilities, a Federal Bureau of Prisons spokesperson told HuffPost.

“Forced labor for low or no wages ― we have a term for that,” said Angela Hanks, a criminal justice expert with the Center for Law and Social Policy. “We call it slavery.”

The Bureau of Prisons requires all able-bodied inmates to work, as do many state corrections agencies (which house the majority of the prison population). There are 1.5 million Americans locked up in state and federal prisons, and 61 percent them had jobs, according to a 2014 survey.

HuffPost readers: Do you have information about the 2018 prison strike or experience working in prison? Tell us about it ― email arthur@huffpost.com. Please include your phone number if you’re willing to be interviewed.

Prison labor is typically justified as a way to rehabilitate criminals, but it’s also always been a way to save the government money. In 1825, New York lawmakers stipulated that prison costs should “be supported wholly, or as nearly as shall be practicable, by the labor of prisoners,” according to a 2004 paper by the economists Frederick W. Derrick, Charles E. Scott and Thomas Hutson.

In 1865, lawmakers amended the U.S. Constitution to outlaw slavery “except as a punishment for crime whereof the party shall have been duly convicted.” At that point, Southern states began to lease out convicts to private firms, essentially perpetuating slavery. Many Southern states continued their convict-lease programs into the early 20th century.

The federal pay rates haven’t increased in at least two decades, even as the federal minimum wage has risen from $4.25 in 1991 to $7.25 as of 2009. Courts have held that prisoners are not entitled to the same protections as free workers under the Fair Labor Standards Act.

Average wages in state prisons actually declined in recent years, according to the Prison Policy Initiative, as several states eliminated pay for custodial work and cut maximum pay for the few prisoners doing industry work. The states with no pay at all for some prison jobs, according to PPI, are conspicuously Southern: Alabama, Arkansas, Florida, Georgia, Mississippi, South Carolina and Texas.

The most common argument against prison labor is that giving jobs to inmates is essentially “stealing” jobs from the private sector. Even though federal agencies are FPI’s only customers, for example, every dollar the government spends on a prison-made product is still a dollar not spent on something that could have been produced by a free person. Economists generally say, however, that because prison labor is so much less efficient than private sector work, owing to things like security costs and the lower education levels of the prison workforce, that its effect on free labor markets is minimal.

The simplest argument against prison labor is that being locked up is itself supposed to be a prisoner’s punishment. Hanks said the fact that prison labor has roots in the convict-lease system is evidence that prison labor is exploitive.

“This is a system that’s designed to be about oppression, and we’re still using it today,” she said.